INFLUENCE OF COMPOST ADDITION TO SOIL ON THE BEHAVIOR OF HERBICIDES

The transformations of eight herbicides (atrazine, simazine, terbutryn , pendimethalin, carbetamide, 2,4-D, metsulfuron-methyl and dimefuron) in soil after compost addition were monitored during long-term labora tory incubations. The herbicides were applied to soil, compost and soi l-compost mixtures. Herbicide sorption, their kinetics of mineralisati on and the extractability of residues were compared in the different t reatments. Compost addition to soil generally decreased herbicide mine ralisation and favoured the stabilisation of herbicide residues. A fra ction of the stabilised residues remained extractable and potentially available. However, most of them were unextractable and formed bound r esidues. Sorption could be at the origin of a kinetically limited biod egradation, mainly for the most highly-sorbed herbicides (atrazine, si mazine, terbutryn, pendimethalin and dimefuron). Compost addition had little effects on the less sorbed herbicides (carbetamide, 2,4-D and m etsulfuron- methyl).